Heat Pump Hot Water Cylinders | What You Need to Know | EcoSphere Energy
Installation Guide · Domestic Hot Water
Heat Pump Hot Water Cylinders Explained
Air source heat pumps can’t connect directly to your existing hot water tank. A dedicated hot water cylinder is required. Here’s everything you need to know.
Why Heat Pumps Need a New Hot Water Cylinder
A standard unvented or vented cylinder is designed for high-temperature boiler systems. Heat pump cylinders are different.
Larger Volume
Because heat pumps heat water more slowly than gas boilers, the cylinder needs to be larger — typically 180–250 litres for most UK homes. This ensures you never run short of hot water.
Large Coil Design
Heat pump cylinders have a large internal coil to transfer heat efficiently at low flow temperatures. Standard cylinders have a small coil designed for boiler temperatures and will be inefficient.
Immersion Backup
A built-in electric immersion heater provides backup hot water if the heat pump needs maintenance, and can top up the cylinder on cold days at peak demand.
Choosing the Right Cylinder Size
Cylinder sizing depends on household size, usage patterns, and the heat pump’s heating capacity.
1–2 People
150–180 litres is usually sufficient. A smaller cylinder charges faster and wastes less standby heat.
3–4 People
200–250 litres is the most common size. This provides ample hot water for morning showers and a bath without the heat pump running continuously.
Larger Homes
300+ litre cylinders are available for homes with 5+ occupants, multiple bathrooms, or high hot water demand. Twin-coil versions can also accept solar thermal input.
Included in Your Installation
Cylinder Costs Are Grant-Eligible
The Boiler Upgrade Scheme grant covers the full heat pump installation, including the hot water cylinder. Oil and LPG homes can receive up to £9,000 toward the complete system cost.
Check your eligibilityGet a Free Quote — Cylinder Included
Every EcoSphere Energy quote includes the hot water cylinder, installation, and full MCS commissioning. No hidden extras.